The two major purposes of this study are: 1) to test a modified version of McCoy and Inciardi's model for determinants of HIV sexual risky behavior of drug users, and 2) to identify homogenous subgroups of HIV risky sexual behaviors of drug users. The study will examine men and women intravenous drug users (IDUs) and non- intravenous drug users that engage in HIV sexual risky behaviors. This study will utilize secondary data analysis of a demonstration project funded by the National Institute on Drug Abuse (NIDA) entitled "St. Louis' Effort to Reduce the Spread of AIDS among IDUs" (ERSA). The ERSA project's primary goal was to attract drug users into substance abuse treatment and educate persons about changing high risk behaviors. Specific Aims: 1) Confirm Inciardi and McCoy's theoretical model for determinants of HIV sexual risky behaviors in a diverse sample of injection and non-injection male and female drug users using structural equation modeling; 2) Identify HIV sexual risky behavior profiles of sub-groups within the sample of IDUs and non-IDUs through the use of LCA and determine the homogeneity of these sub-groups over the 18 month longitudinal follow-up; 2a) Compare the HIV sexual behavior profiles of IDUs to non-IDUs both at a baseline and over the 18 month longitudinal follow-up; and 2b) Compare the HIV sexual risky behavior profiles of males and females within the sample both at baseline and over the 18 month longitudinal follow-up.